Advanced Geophysical Measurement Methods Using Engineered Fiber Optic Acoustic Sensor

Distributed Acoustic Sensing (DAS) technology enables advanced geophysical measurement methods, where the fibre optic cable is deployed as a dense, wide-aperture phase-array sensor in novel configurations. A sensing system has recently been developed that combines an engineered fiber with bright scatter centers with a low-noise, wide dynamic-range optoelectronics DAS interrogator. This enhanced DAS with engineered fiber offers a 20dB (100x) improvement in sensitivity and dynamic range compared to that achieved with standard fiber. The new DAS technology seeks to disrupt conventional geophysical surveying methods, and so enable the realisation of new applications. In unconventional wells, in addition to seismic and microseismic measurements, the improved low frequency response of the DAS system, down to the milli-Hertz level, is used to monitor hydraulically induced strain effects. In offshore applications, the permanent installation of the fiber optic along production and injection wells is enabling more frequent and cost-effective seismic data to be acquired. The next challenge is stepping out to subsea wells. We present some initial lab results demonstrating the benefits of the engineered fiber for advanced seismic acquisition in long-tie back subsea wells using only surface optoelectronics.